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Bureau of Mines Information Circular/ 1985 



Improved Fire Protection for Underground 
Fuel Storage and Fuel Transfer Areas 

By William H. Pomroy and Guy A. Johnson 




03 



UNITED STATES DEPARTMENT OF THE INTERIOR 



C75j 

'Wines 75th an^ 



Information Circular 9032 



Improved Fire Protection for Underground 
Fuel Storage and Fuel Transfer Areas 

By William H. Pomroy and Guy A. Johnson 




UNITED STATES DEPARTMENT OF THE INTERIOR 

Donald Paul Hodel, Secretary 

BUREAU OF MINES 
Robert C. Horton, Director 







4* 



{V 



Library of Congress Cataloging in Publication Data: 

i — 1 



Pomroy, William H 

Improved fire protection for underground fuel storage and fuel trans- 
fer areas. 

(Information circular / United States Department of the Interior, Bureau of Mines; 9032) 

Bibliography. 

Supt. of Docs.: 128.27 

1. Mine fires— Prevention and control. 2. Petroleum products— Underground storage 
— Fires and fire prevention. 

I. Johnson, Guy A. II. Title. III. Series: Information circular (United States. Bureau of 
Mines; 9032) 

TN295.U4 [TN315] 622s [622's.8] 84—600269 









CONTENTS 



Abstract 

Introduction 

Analysis of fueling system fire hazards 

Methodology 

Results 

Guidelines for safe fueling system design 

Fuel storage area 

Fuel transfer area 

Discussion 

Generic fire sensing and suppression system. . . 

Design concepts 

Fuel transfer area 

Suppression 

Controls 

Detection 

Fuel storage area 

Suppression 

Controls 

Detection 

Additional design considerations 

System reliability and maintenance. 
Reliability of individual components. 
System complexity 



Page 

1 
1 
1 
2 
2 
3 
3 
4 
4 
4 
4 
4 
4 
5 
5 
5 
5 
5 
5 
9 
9 
9 
9 



Page 



Costs 9 

Alternative system designs 10 

Prototype fire sensing and suppression system. . . 10 

General description 10 

Suppression 10 

AFFF subsystem 10 

Dry chemical subsystem 11 

Detection and control 11 

Tests 12 

Laboratory component testing 12 

Suppression 12 

Detection and control 12 

Laboratory full-scale fire testing of 

complete system 12 

Field test 12 

Installation, inspection, and pretests. 12 

Fire testing 15 

Studies of alternative system 'designs 18 

Cost-effectiveness analysis 18 

System cost versus fire cost 18 

Cost-performance tradeoffs between systems. 18 

Summary 19 



ILLUSTRATIONS 



1 . Recommended fueling system design 3 

2. Recommended fuel transfer area fire sensing and suppression system 6 

3. Recommended fuel storage area fire sensing and suppression system utilizing AFFF suppressant 6 

4. Recommended fuel storage area fire sensing and suppression system utilizing high-expansion foam 

suppressant 7 

5. Recommended fuel storage area fire sensing and suppressant system utilizing Halon 1301 suppressant 7 

6. Recommended fuel storage area fire sensing and suppression system utilizing dry chemical suppressant ... 8 

7. Recommended fuel storage area fire sensing and suppression system utilizing twin-agent suppressant 8 

8. Idealized failure rate curve 9 

9. Prototype fire sensing and suppression system for underground fuel storage and transfer area 11 

10. Configuration of system elements for mockup testing 13 

11. Twin-agent discharge during mockup testing 13 

12. System control panel 14 

13. Ultraviolet flame detector head 14 

14. Twin-agent suppression subsystem 14 

15. Dry chemical nozzle with blowoff cap 14 

16. Foam-water sprinkler nozzle 15 

17. Vehicle mockup in fuel transfer area 15 

18. Igniting test fire beneath vehicle mockup 16 

19. Test fire burning under mockup 16 

20. Twin-agent discharge onto test fire 17 

21 . Test fire fully extinguished 17 

TABLES 

1 . Hazard ranking of potential leak and spill sources 2 

2. Hazard ranking of potential ignition sources 2 

3 Fueling subsystem hazard indexes 2 

4. System cost comparisons 10 

5. Test site description 14 

6. Cost-effectiveness matrix for fueling area fire protection systems 19 





UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT 


A 


ampere 


min 


minute 


°F 


degree Fahrenheit 


pet 


percent 


fpm 


foot per minute 


pct/yr 


percent per year 


ft 


foot 


ppm 


parts per million 


gal 


gallon 


psi 


pound per square inch 


gpm 


gallon per minute 


s 


second 


gpm/sq ft 


gallon per minute per square foot 


sq ft 


square foot 


h 


hour 


V 


volt 


in 


inch 


V dc 


volt, direct current 


lb 


pound 


yr 


year 


Ibf 


pound (force) 


W 


watt 


Ibf/s 


pound (force) per second 


wt pet 


weight percent 


mg/L 


milligram per liter 







IMPROVED FIRE PROTECTION FOR UNDERGROUND FUEL 
STORAGE AND FUEL TRANSFER AREAS 



By William H. Pomroy 1 and Guy A. Johnson 1 



ABSTRACT 



The potential for large-scale fires in underground fuel storage and fuel transfer areas 
prompted the Bureau of Mines to study fire hazards in these areas and devise improved 
fire safety technology for use in these areas. This report describes the Bureau's research 
to characterize and quantify fire hazards in fuel storage and fuel transfer areas, develop 
guidelines for safe and efficient fueling system design, prepare specifications for automatic 
fire sensing and suppression systems for these areas, test prototype systems in the 
laboratory and in underground mines, and perform cost-effectiveness evaluations of the 
devised technology. 



INTRODUCTION 



From the early 1950's through the mid-1960's, 
underground mining was revolutionized by the introduction 
of mobile rubber-tired diesel-powered equipment. Entirely 
new and highly productive mining systems were developed 
based on the concept of "trackless" mining. The increasing 
use of trackless equipment, however, was accompanied by 
an increasing frequency of diesel equipment fires. Fires in- 
volving rubber, oil. hydraulic fluid, grease, and diesel fuel in- 
creased 557 pet from the 1950-64 period to the 1965-79 
period. Mobile equipment was involved in less than 10 pet 
of all underground metal and nonmetal mine fires from 1950 
to 1967 but was involved in about 40 pet of all such fires from 
1968 to 1979. In response to this growing hazard, the Bureau 
initiated a research program aimed at improving fire protec- 
tion technology for underground metal and nonmetal trackless 
mining operations. The Bureau's research to develop 
automatic fire protection systems for underground mobile 
equipment is described in Information Circular 8954. 2 

In addition to fire hazards on vehicles, mobile equipment 
servicing facilities such as underground shops, maintenance 
bays, and fuel storage and transfer areas also present a 
significant fire hazard. These areas are characterized by the 
presence of combustible materials such as lubricating oils, 



greases, starting fluids, solvents, hydraulic oils, and diesel 
fuel; ignition sources such as hot engine surfaces and elec- 
trical, cutting, and welding equipment; and constant vehicular 
traffic. Fuel storage areas, which provide bulk storage in both 
tanks and drums, and transfer areas, where vehicle refuel- 
ing takes place, are particularly critical because of their poten- 
tial for the involvement of very large quantities of diesel fuel, 
lubricating oils, and hydraulic fluids in a fast-growing, high- 
energy fire. 

Although no large-scale fires in underground fuel storage 
or transfer areas have yet been reported, the potential 
seriousness of such fires prompted the Bureau to embark on 
research to upgrade the overall level of fire safety technology 
for these areas. The research began with a comprehensive 
fire hazards analysis. The results of this analysis were then 
used to establish (1) guidelines for the design of safe and 
efficient underground fuel storage and transfer areas and (2) 
specifications for automatic fire sensing and suppression 
systems for fueling areas. Prototype fire sensing and sup- 
pression equipment was fabricated, then laboratory and field 
tested. All work was accomplished under a contract with the 
Ansul Co. of Marinette, Wl. 3 



ANALYSIS OF FUELING SYSTEM FIRE HAZARDS 



Guidelines for the construction of safe fuel storage and 
transfer areas and design specifications for fire protection 
systems for these areas were based on data acquired through 



a comprehensive and detailed analysis of fueling area fire 
hazards. Data sources included Bureau experts and experts 
employed by the Mine Safety and Health Administration 



rervisory mining engineer. Twin Cities Research Center. Bureau of 
leapotis. MN 
'Johnson. G A Automatic Fire Protection for Mobile Underground Mining 
Equipment. BuMines IC 8954. 1983. 12 pp. 



3 Ansul Co. Improved Fire Protection System for Underground Fueling Areas 
(contract H0262023) Volume 1: BuMines OFR 120-78, 1977, 325 pp ; 
NTIS PB 288 298/AS Volume 2: BuMines OFR 160-82, 1981, 111 pp .; 
NTISPB83 114744. 



(MSHA); private consultants; management, safety, and 
maintenance personnel from several underground mines; 
equipment manufacturers; and insurance industry represen- 
tatives. In addition, researchers visited 16 underground mines 
to observe fuel storage and transfer area designs and safety 
practices. 



METHODOLOGY 

Although the designs of existing fuel storage and transfer 
areas are based on the unique experiences of their designers 
and the specific needs of individual mining operations, cer- 
tain features were common to many of the systems observed. 
These features, or subsystems, are listed below. 

1 . Surface storage 

2. Surface transport 

3. Shaft transport 

4. Borehole transport 

5. Transport to underground storage 

6. Underground storage 

7. Transport to fuel transfer area 

8. Fuel transfer 

An expert panel was convened to rank the hazard 
associated with each subsystem. The panel consisted of (1) 
an experienced mine fire hazards analyst who had visited six 
of the mines in the study, (2) an experienced mine fire hazards 
analyst who had visited all of the mines in the study, (3) a 
mining engineering consultant, (4) a petroleum systems 
design consultant, and (5) a hydraulic systems research and 
design specialist. 

The panel evaluated the eight generic subsystems listed 
above as well as the design of each system, subsystem, and 
major component observed at the 16 mines studied. The fire 
hazard of each subsystem was evaluated in terms of (1) leak 
or spill potential and (2) ignition potential. Potential sources 
of leaks and/or spills and potential ignition sources were iden- 
tified and ranked by each panel member. The individual rank- 
ings were averaged to yield overall hazard rankings for each 
leak or spill and ignition source. The potential range of hazard 
rankings was from 1 (most hazardous) to 13 (least hazardous). 



RESULTS 

Results of the analysis of the potential for fuel leaks and 
spills are shown in table 1. 

The three components most likely to leak or cause a spill 
are the hose to the vehicle, the pump to the vehicle, and the 
piping to the vehicle fueling pump. All three of these com- 
ponents are situated in the fuel transfer area. Shaft and 
haulageway piping follow as the next most hazardous com- 
ponents in terms of leaks and spills. 

Results of the analysis of the potential ignition sources are 
shown in table 2. 

Six of the thirteen ignition sources identified, including the 
three most hazardous sources, occur in the fuel transfer area. 

A hazard index reflecting the relative fire hazardousness 
of each fueling subsystem was derived by combining the leak 
and spill and ignition potential rankings. Hazard indexes for 
the eight generic fueling subsystems are shown in table 3 
in decending order of hazardousness. 

As might be expected from the analysis of leak and spill 
and ignition source potentials, the fuel transfer area was 



TABLE 1 . — Hazard ranking of potential leak and 
spill sources 



Fueling system component 



Hazard ranking 1 



Hose to vehicle 

Underground pump to vehicle 

Piping to fueling pump 

Shaft piping valves 

Haulageway piping 

Haulageway valves 

Surface transfer pump 

Shaft piping 

Urn rground storage tanks 

Surface storage tanks 

Surface piping 

Haulageway pumps 

Nozzles 

1 1 = most hazardous; 13 = least hazardous. 



TABLE 2. — Hazard ranking of potential 
ignition sources 



2.3 
4.5 
5.1 
6.5 
6.7 
6.8 
7.0 
7.1 
7.3 
8.3 
8.4 
8.5 
12.8 



Source 



Hazard ranking 1 



Electrical sparks from vehicle 

Vehicle engine heat 

Electrical sparks from refueling area 

Smoking 

Impact sparks (from vehicle-rib impacts) .... 

Welding 

Vehicle exhaust 

Human error 

Hot hydraulic pumps 

Drive shaft brakes 

Unusual occurrences 

Trash build-up 

Spontaneous combustion 

1 1 = most hazardous; 13 = least hazardous. 



TABLE 3. — Fueling subsystem hazard indexes 



2.2 
2.6 
3.6 
4.4 
5.3 
7.5 
8.6 
8.6 
8.6 
8.7 
8.7 
8.8 
8.8 



Index 1 



278 
217 
101 
77 
59 
50 
48 
43 



Subsystem 

Fuel transfer area 

Underground storage area 

Surface storage area 

Shaft transport 

Surface transport 

Borehole transport 

Transport to fuel transfer area 

Transport to underground storage area. . . . 

1 Highest values indicate most hazardous subsystems. 



judged to be the most hazardous. Both the probability of a 
fuel spill and the probability of ignition are highest in this area. 
Underground fuel storage was ranked as the second most 
hazardous subsystems. However, although the likelihood of 
a fire occurring in the storage area is less (than in the fuel 
transfer area), the magnitude of a fire in the storage area 
would be far greater. 

Fuel transfer areas where fuel tanks and drums are pres- 
ent are more hazardous than areas where only a fueling noz- 
zle is present. The panel agreed that the most likely underly- 
ing cause of a fire is operator error, including such unsafe 
practices as smoking while refueling, overfilling fuel tanks, 
insufficient precautions during welding in the refueling area, 
unsafe or careless operation of vehicles, and failure to prop- 
erly maintain and inspect vehicles and/or refueling 
equipment. 



GUIDELINES FOR SAFE FUELING SYSTEM DESIGN 



Fueling system designs should be aimed at mitigating the 
conditions identified in the hazards analysis as contributing 
to the occurrence or severity of fueling system fires. Designs 
that require a minimum of operator skill are preferred because 
their use can help minimize operator error. Designs that 
physically separate the vehicles being refueled from the fuel 
storage area are preferred because they minimize contact 
between the fuel source and the ignition source. Designs that 
limit line pressures and have a low risk of tank overfilling are 
preferred because three features can help minimize leaks and 
spills. The recommended fueling system design is shown in 
figure 1 . and the design features illustrated in this figure are 
discussed in the next two sections. 



FUEL STORAGE AREA 

Surface storage tanks should be designed and constructed 
in accordance with applicable industry standards. Combusti- 
ble liquids should not be pumped underground from a large 
storage tank; instead they should be pumped from a batch 
tank with less capacity than the underground tank being filled. 
Borehole transport is preferred over shaft transport. Exhaust 
from the fuel storage area should be directed to a return. 
Automatic fire sensing and suppression systems (which are 
discussed in detail in the next main section of this report) are 
recommended, as are hand portable fire extinguishers. 

A major concern in underground fueling system design is 
whether to use a wet or a dry transfer line between surface 



storage and the underground location. A wet line, with fuel 
in it at all times is advantageous because it makes 
underground storage of fuel unnecessary. A dry line, used 
to periodically resupply underground tanks, has the advan- 
tage of placing far less stress on piping and fittings. A hazards 
analysis indicated that the overall hazard was generally slight- 
ly less with the dry-line system; however, both systems are 
acceptable. When choosing between wet and dry transfer 
lines, local conditions such as type of piping used, length of 
drop, length of horizontal pipe run from borehole to fuel 
storage and/or transfer area, frequency of fuel transfers, and 
the design and layout of the fuel storage and transfer areas 
should be considered. 

Underground storage areas should be fully enclosed and 
constructed of materials having a fire resistance rating of at 
least 2 h. Windows should close automatically with fusible 
links, and the door should remain closed when not in use. 
The floor should be impermeable (rock or concrete) and have 
a sump for holding spilled fuel. Lights and wiring should be 
explosion proof. 

The tanks should be of good quality and supported on con- 
crete saddles. An overflow vent pipe large enough to release 
fuel at the maximum possible delivery rate is recommended 
to avoid rupture during a possible overfill. This vent should 
also release pressure in the event of a fire. The overflow vent 
should feed into an overflow tank equipped with an alarm. 
Tanks should have a float or sight glass with the refill level 
clearly marked to reduce human error. 



Mam storoge tank 



Impoundment^^ * 



Batch transfer tank 
Explosion-proof or 
air pump 



Positive-displacement pump 




-■atic-^ Sloped concrete pod 
shutoff >. r spill trough 

nozzle 



iump pump and tank 



Fire-resistant bulkhead with steel 
door, self-closing windows, ond 
automatic-shutof f ventilation fan 



FIGURE 1.— Recommended fueling system design (fuel storage area, top and lower right, and fuel transfer 
area, lower left; fire sensing and suppression system not shown). 



FUEL TRANSFER AREA 

There should be no fuel or oil tanks or drums within 50 ft 
of the fuel transfer area (by shortest accessible route) unless 
such tanks or drums are enclosed in a fire-resistant struc- 
ture. Emergency pump controls should be located so they 
can be quickly reached in the event of fire. The area should 
be well lighted with explosion-proof lamps. As was recom- 
mended for fuel storage areas, exhaust from the fuel transfer 
area should be directed to a return. Again, automatic fire 
sensing and suppression systems and hand portable fire ex- 
tinguishers are also recommended. 

Diking or some other form of drainage control should be 
provided to collect spilled fuel into a container with minimum 
surface area. A means for absorbing spilled fuel should be 
located near the nozzles. Fuel transfer areas should not be 
located where spills would drain toward an underground 
storage area or shop. 

Pumps should be located outside the underground storage 
area to remove that potential ignition source from the stored 
fuel. The pump should not keep constant pressure in the fuel 



lines; it should instead be actuated by the operator during 
the fueling operation. Automatic shutoff nozzles are recom- 
mended to reduce the incidence of overfills. An excess-flow 
valve should be installed downstream of the pump. The area 
should be kept as clean and orderly as possible. 



DISCUSSION 

The preceding guidelines for safe fueling system design 
represent an optimum rather than a minimum approach. They 
are based on certain assumptions regarding aspects of mine 
design that are considered commonplace in the North 
American metal and nonmetal mining industry. Alternative 
systems and subsystem elements may result in the same or 
a higher level of safety depending on local conditions. As ex- 
amples, the transport of fuel in portable tanks instead of fix- 
ed piping is warranted in adit mines, and fuel storage and 
fuel transfer areas situated near an exhaust shaft and ven- 
tilated directly to the return need not be enclosed or protected 
by suppression systems. 



GENERIC FIRE SENSING AND SUPPRESSION SYSTEM 



DESIGN CONCEPTS 

The development of generic fire sensing and suppression 
system design concepts was guided by the analysis of fuel- 
ing system fire hazards. Designs were developed for the fuel 
transfer area and the underground storage area, which were 
ranked as the first and second most hazardous fueling sub- 
systems (table 3). 

Many different fire suppression systems are currently used 
to protect underground fuel transfer and storage areas against 
fires. Due to the many variations in fueling systems designs, 
no single fire suppression system can be recommended for 
all applications. Each hazard requires its own analysis and 
a design concept developed to specifically address that 
hazard. However, certain general principles of fire protection, 
such as the suitability of suppressant agents on various fuels 
and the properties of various detection devices, apply 
regardless of the hazard under consideration. Therefore, 
these general principles were applied together with the 
guidelines for safe fueling system design to develop the 
generic design concepts for fueling area fire protection 
systems. The resultant design concepts are discussed in the 
following sections in the context of these principles and 
guidelines. 

Fuel Transfer Area 

The generic fuel transfer area fire protection system con- 
sists of three elements: suppression, controls, and detection. 

Suppression 

Five suppressants were considered for possible use in the 
fuel transfer area fire suppression system: aqueous film- 
forming foam (AFFF), water, high-expansion foam, Halon 
1301 4 halogenated fire extinguishing agent, and multipurpose 
dry chemical. Agents eliminated from consideration includ- 



4 Reference to specific products does not imply endorsement by the Bureau 
of Mines. 



ed carbon dioxide and Halon 121 1 , because of possible safety 
hazards to personnel who might be exposed to the agents 
in a confined area; protein and synthetic foams because they 
are incompatible with dry chemical, require special air- 
aspirating equipment, have limited stability, and require 
higher discharge rates than AFFF; and ordinary dry chemicals 
because they are unable to extinguish ordinary combustibles 
such as paper, rags, and wood. 

A tradeoff study of the capabilities and limitations of the 
five suppressants was conducted. Based on this study, no 
single suppressant emerged as having optimum fire ex- 
tinguishing capabilities in all possible situations. The selec- 
tion of a suppressant for a particular application is influenced 
by all of the following factors: fueling area design, enclosure 
integrity, physical dimensions, and location in the mine; 
airflow and air velocity through the area; types of fires ex- 
pected; and possible effects on personnel. The factor that 
has the greatest impact on suppressant effectiveness is ven- 
tilation. In completely enclosed areas with no ventilation, 
AFFF, high-expansion foam, and Halon 1301 can be used 
to effectively extinguish a typical combustible-liquid spill fire 
and secure the fuel against reignition. However, under the 
conditions of moderate-to-high ventilation, which are typical 
of most fuel transfer areas, only AFFF can extinguish and 
secure a spill fire. 

Another important factor influencing suppressant selection 
is the type of fire expected. In addition to spill fires, 
combustible-liquid pressure fires and running-fuel fires, as 
well as fires involving ordinary combustibles, could occur in 
a typical fuel transfer area. 

No single agent is completely effective in extinguishing and 
securing all of these types of fires, especially when the area 
is subject to moderate-to-high ventilation. Under this worst- 
case condition, a combination of suppressants is required 
for total protection. 

The most effective combination of agents is AFFF and 
multipurpose dry chemical. The dry chemical achieves quick 
"knockdown" of the initial flame. The AFFF forms a fast- 
spreading film over the spilled fuel, preventing the escape 



of flammable vapors and thereby eliminating the possibility 
of reignition. This type of "twin-agent" system, utilizing AFFF 
and multipurpose dry chemical, is commonly used at airports, 
petrochemical plants, and in other high-hazard facilities where 
flammable and combustible liquids are present. 

Controls 

System control options include manual operation, 
automatic operation, and automatic operation with manual 
override. A manually operated system could use hand por- 
table extinguishers, hose reels, and/or an overhead network 
of fixed piping and nozzles for suppressant distribution; 
whereas automatic and automatic-with-manual-override 
systems would use only fixed piping and nozzles. However, 
installation of a fixed suppression system does not eliminate 
the need to provide hand portable extinguishers in the area. 

The most important criterion in selecting a system control 
is extinguishing response time. Rapid extinguishment is 
critical for several reasons: 

1 . The longer the preburn time (elapsed time between ig- 
nition and attempted extinguishment), the more difficult ex- 
tinguishment becomes. Fuels are heated to temperatures 
above their flashpoints, and involved surfaces become poten- 
tial sources for reignition (after fire-suppressant discharge). 
Secondary combustibles, such as wood or rags may be ig- 
nited and the fire may grow in size and area beyond the limits 
of suppression system coverage. 

2. The fire may block safe egress of personnel, or person- 
nel may be injured and threatened by the fire directly. 

3. Finally, as long as the fire is permitted to burn, copious 
amounts of toxic combustion products, such as carbon 
monoxide, are generated. 

Manually operated suppression systems depend on the 
prompt and appropriate response of attending personnel. If 
personnel are not present, or if they panic or are injured, ac- 
tivation of the suppression system may be delayed to the point 
where extinguishment cannot be assured. Worse, the system 
may not be activated at all. 

Automatic system operation offers a higher level of pro- 
tection than manual operation. Automatic control with the 
added security of a manual override capability is the recom- 
mended option. Although the potential for false alarms exists 
with automatic operation, the seriousness of an uncontrol- 
led fueling area fire justifies this remote risk. 

Detection 

Automatic system operation requires the use of a detec- 
tion system to trigger discharge of the suppressant. Detec- 
tion options considered included heat, smoke, and flame. 

Heat, or thermal, detectors, which depend on convected 
thermal energy for alarm activation, have a proven history 
of high reliability and low maintenance requirements, even 
when used in harsh environments. However, the response 
of thermal sensors may be unacceptably slow, especially in 
areas subject to moderate-to-high ventilation. 

Smoke detector responses are typically much faster, but 
as with thermal detectors, response is affected by local air 
currents. In addition, nuisance alarms can be expected to 
result from dust accumulations, humidity changes, and ex- 
posure to blasting fumes and diesel exhaust. 

Flame detectors offer the fastest response possible. They 
are designed to respond to the infrared, visible, and/or 
ultraviolet light emitted by a fire. Ultraviolet and infrared detec- 
tors are routinely used in rugged industrial settings such as 
offshore oil platforms, petrochemical plants, and aircraft 



hangars. Maintenance is generally confined to cleaning the 
optical lenses. Typical sources of nuisance alarms include 
lighting and arc welding for ultraviolet detectors and hot sur- 
faces or gases for infrared detectors. 

Ultraviolet detection is recommended for fuel transfer area 
fire protection systems. Thermal detection was ruled out 
because it is inherently slower than the other methods. In 
moderately to highly ventilated areas, detection delays would 
permit excessive preburn times. Smoke detection was ruled 
out because frequent nuisance alarms would result from con- 
stant vehicular traffic. Infrared detectors were rejected 
because false alarms could be triggered by hot engine sur- 
faces and exhaust gases. Ultraviolet detection therefore pro- 
vides the fastest and most reliable fire signal. Although arc 
welding within the optical field of view of an ultraviolet detector 
could cause a false alarm, such an occurrence could be 
avoided by disabling the detection system while the welding 
operation is performed. 

Figure 2 illustrates the recommended design concept for 
the fuel transfer area fire sensing and suppression system. 
This concept features twin-agent suppression, ultraviolet 
flame detection, and automatic-with-manual-override control. 

Fuel Storage Area 

The storage area fire protection system also consists of 
suppression, control, and detection subsystems. 

Suppression 

As discussed previously, AFFF, high-expansion foam, and 
Halon 1301 are all effective in extinguishing and securing a 
typical combustible-liquid spill fire in unventilated areas such 
as a completely enclosed fuel storage area. Although dry 
chemical is not capable of securing combustible liquids 
against reignition, its overall suppressant rating is higher than 
those of AFFF and high-expansion foam because of its 
greater extinguishing effectiveness on combustible-liquid 
pressure and running-fuel fires. All four agents are considered 
acceptable for this application; however, for optimum protec- 
tion, an AFFF and dry chemical twin-agent system is required. 

Controls 

The same system control options as were discussed for 
the fuel transfer area— manual, automatic, and automatic with 
manual override — exist for the storage area. The same selec- 
tion criteria apply as well. Again, the overall level of safety 
is higher with automatic operation than with manual opera- 
tion, and the optimum system would provide the added securi- 
ty of a manual override discharge capability. Such an op- 
timum system will minimize preburn time, heating of involv- 
ed surfaces, ignition of secondary combustibles, fire spread, 
and the generation of toxic products of combustion. 

Detection 

Because the fuel storage area is completely enclosed, 
fewer constraints are imposed on detector selection. Although 
thermal detection is inherently slower than smoke or flame 
detection, acceptable response times could be achieved with 
a properly designed thermal detection system in this area. 
Smoke detection would also be acceptable, however, op- 
timum system performance requires flame detection. Either 
infrared or ultraviolet detection could be used. 

Figures 3 through 7 show recommended fuel storage area 
fire sensing and suppression system layouts utilizing AFFF, 
high-expansion foam, Halon 1301, dry chemical, and twin- 
agent suppressant, respectively. Each system depicted in- 




KEY 
/ Nitrogen cylinders 

2 Dry chemical tank 

3 Diaphragm foam tank 

4 Control box 

5 Dry chemical nozzle 

6 Detector 

7 Detector wiring 

8 Foam-water sprinkler head 

9 Balanced distribution piping 

10 Emergency power supply 
// Visual and audible warnings 

12 To remote warnings 

13 Pneumatically operated main valve control 

14 Manual actuation 

15 Rat io control ler 

16 Mine water supply line 



FIGURE 2.— Recommended fuel transfer area fire sensing and suppression system. 




KEY 
/ Diaphragm foam tank 

2 Pneumatically operated main control valve 

3 Rat io control ler 

4 Balanced distribution piping 

5 Foam-water sprinkler head 

6 Mine water supply line 

7 Manua I actuation 

8 Control box 

9 Emergency power supply 
IO Visual and audible warnings 
// To remote warnings 

12 Detector 

13 Detector wiring 



FIGURE 3.— Recommended fuel storage area fire sensing and suppression system utilizing AFFF suppressant. 





// 







KEY 






/ 


Diaphragm 


foam tank 






2 


Pneumatically operated 


main 


control valve 


3 


Foam generator 






4 


Mine water 


supply line 






5 


Manual act 


uot ion' 






6 


Control box 






7 


Emergency 


power supp 


iy 




8 


Visual and 


audible warn i ng 




9 


To remote 


wa r nings 






10 


Detector 









V 



// Detector wiring 



FIGURE 4.— Recommended fuel storage area fire sensing and suppression system utilizing high-expansion 

foam suppressant. 




KEY 

iced distribution piping 

nozzle 
let manifold 

4 Halon tank 

5 Manual actuation 

6 Control box 

7 Emergency power supply 

8 Visual ond audible warnings 

9 To remote warnings 
10 Detector 
// Detector wiring 

FIGURE 5— Recommended fuel storage area fire sensing and suppression system utilizing Halon 1301 
suppressant. 







KEY 
/ Balanced distribution piping 
2 Dry chemical nozzle 
J Nitrogen cylinder 

4 Dry chemical tank 

5 Manual actuation 

6 Control box 

7 Emergency power supply 

8 Visual and audible warnings 

9 To remote warnings 
10 Detector 
/ / Detector wi r ing 

FIGURE 6.— Recommended fuel storage area fire sensing and suppression system utilizing dry chemical 
suppressant. 

12 13 




KEY 
en cylinders 
emical tank 
agm foam tank 

actuation 
I box 

ency power supply 
and audible warnings 
mote warnings 
atically operated main 
rol valve 
control ler 
emical nozzle 
ed distribution pi ping 
or 

or wiring 

water sprinkler head 
16 Mine water supply line 

FIGURE 7.— Recommended fuel storage area fire sensing and suppression system utilizing twin-agent 
suppressant. 



eludes ultraviolet flame detection; however, as noted above, 
thermal, smoke, or infrared flame detection would also be 
acceptable. For AFFF. dry chemical, and twin-agent suppres- 
sion, direct application of suppressant is most effective. Thus, 
numerous nozzles are distributed throughout the hazard area. 
However, Halon 1301 and high-expansion foam quickly ex- 
pand to fill the available enclosure space, making fewer 
discharge points necessary. 

Additional Design Considerations 

The foregoing analysis specifies the basic elements that 
should be included in fire protection systems for underground 
fuel transfer and storage areas. Additional design considera- 
tions relating to reliability, maintenance and system complex- 
ity are discussed below. In a survey of 18 mine managers, 
reliability, maintenance, and costs were identified as the three 
most important criteria for equipment selection. In later sec- 
tions of the report, comparative cost data are presented and 
cost-effectiveness analysis of fire protection systems is 
discussed. 

System Reliability and Maintenance 

Where the proper function of a system depends on the pro- 
per function of all of its components, overall system reliabili- 
ty is expressed as follows: 

RsW = (Rd(t)) x (R c2 (t)) x (R c3 (t)) ... (R cn (t)) 

where R s (t) = system reliability over time interval t 

and R c (t) = component reliability over time interval t. 

Thus, system reliability is maximized when the reliability of 
individual components is maximized and when the number 
of individual components is minimized. 

Reliability of Individual Components 

Individual component reliability generally follows the pat- 
tern shown in the idealized failure rate curve (fig. 8). The in- 
itial period is characterized by a relatively high failure rate 
due to manufacturing and installation defects or applications 
that exceed the recommended duty cycle or environmental 
restrictions of the component. It is sometimes referred to as 
infant mortality. The middle period is characterized by a low 




FIGURE 8.— Idealized failure rate curve. 



failure rate. Failures during this period are the result of ran- 
dom events. It is sometimes referred to as the useful life or 
prime of life. The final period is characterized by a high and 
asymptotically increasing failure rate, which results from com- 
ponents wearing out. This period is sometimes referred to 
as the wearout or burnout phase. 

Careful selection of components, with particular attention 
to manufacturing quality control, rated duty cycles, and en- 
vironmental restrictions can help minimize infant mortality. 
The performance of similar components operated under 
similar conditions can also guide equipment selection. In ad- 
dition, components that are listed or approved by one of the 
various nationally recognized independent testing 
laboratories can be specified. Components are listed or ap- 
proved by these laboratories only after they have been 
thoroughly tested and found to meet or exceed the re- 
quirements of rigorous environmental and operational 
standards. 

Periodic inspection is necessary to detect random failures 
that may occur during the component's useful life. How often 
inspections are necessary is determined through long-term 
observation of the system in operation. The fire sensing and 
suppression systems described above require weekly visual 
checks. Typical inspection items include inspecting nozzles 
for obstructions, checking pressure gauges for pressurized 
components, noting general appearance of components for 
mechanical damage and corrosion, and checking the posi- 
tion of main water-supply valves. 

If component failure is to be avoided, preventive 
maintenance (PM) is necessary to ensure that components 
will be repaired or replaced as necessary before they wear 
out. Manufacturer-recommended PM programs are designed 
to extend the useful life of a component and/or preempt com- 
ponent failure by replacement before wearout failures occur. 
Various components of the fire sensing and suppression 
systems require PM at 6-month, 1-yr, 2-yr, and 5-yr intervals. 

Typical maintenance items include testing suppression 
system actuation mechanisms for proper function and 
pneumatic actuation lines for leaks (no agent discharge re- 
quired); weighing pressurized components and comparing 
to fill levels indicated by pressure gauges; testing detectors 
with test flames; testing all visual and audible alarms and 
other system control features; checking fill levels of non- 
pressurized suppressant-agent containers; and hydrostatic 
testing of pressure vessels. Component repair or replacement 
should be performed when necessary. In addition, conditions 
causing undue wear to components should be corrected if 
possible. 

System Complexity 

The fire sensing and suppression systems discussed are 
as simple and straightforward as could be designed and yet 
still perform as required. As few individual components as 
possible were included in each design. Each system consists 
of predesigned and manufactured modules to simplify 
assembly, installation, inspection, maintenance, and 
operation. 



COSTS 

Costs of detection, suppression, and control equipment 
would vary according to the nature of the hazards that might 
be expected and the size of the area covered by the system. 
Table 4 contains estimated costs for five alternate fire pro- 
tection systems for a typical enclosed fuel storage area 65 



10 



TABLE 4.— System cost comparisons 

(Fire sensing and suppression systems for fuel storage 

and fuel transfer areas using various suppressants; 

estimated costs in 1983 dollars) 

Suppressant 

High-expansion Dry Twin 

AFFF foam Halon 1301 chemical agent 

Equipment $10,600 $10,900 $10,300 $10,300 $16,500 

Installation 4,400 3,000 3,000 5,200 6,100 

Operation 1,500 1,200 2,600 370 3,000 

Maintenance, 

annual 300 300 370 370 500 

Total 16,800 15,400 16,270 17,370 26,100 

AFFF Aqueous film-forming foam. 



ft long, 20 ft wide, and 1 3 ft high, containing 1 ,250 gal of com- 
bustible liquids. A fuel storage area was chosen for this ex- 
ample over a fuel transfer area because only one system type 
(twin agent) was recommended for the transfer area, whereas 
all five types (twin agent, high-expansion foam, Halon 1301 , 
dry chemical, and AFFF) were judged acceptable for the 



storage area. Included in each estimate, as a part of equip- 
ment cost, is $4,400 for detection (ultraviolet flame) and con- 
trol (automatic with manual override). 

The installation cost estimates in table 4 are for installa- 
tions by a fire protection contractor. Significant savings could 
be realized if mine personnel installed the system. 

Overall system cost-effectiveness is discussed in a later 
section of this report. 



ALTERNATIVE SYSTEM DESIGNS 

Like the guidelines for fueling system design, the recom- 
mended conceptual designs for fuel transfer area and fuel 
storage area fire protection systems represent optimum rather 
than minimum approaches. Also, these concepts are based 
on certain assumptions regarding the layout of the fueling 
area, such as fuel transfer area ventilation, storage area 
enclosure, etc. Alternative system elements may result in a 
higher level of safety depending on local conditions. However, 
the rationales presented in this report for selecting system 
elements can provide useful guidance if alternatives are 
considered. 



PROTOTYPE FIRE SENSING AND SUPPRESSION SYSTEM 



A complete fire sensing and suppression system was 
designed, fabricated, and tested under laboratory conditions 
and in an underground mine to evaluate the feasibility, prac- 
ticality, and overall effectiveness of the system under 
simulated and actual mining conditions. 



GENERAL DESCRIPTION 

The prototype fire sensing and suppression system (fig. 
9) was designed in accordance with the generic design con- 
cepts discussed previously. Each system element is dis- 
cussed in detail below. 

Suppression 

Since the site selected for in-mine tests was not enclosed 
and combined both storage and transfer of fuel, a twin-agent 
AFFF and multipurpose dry chemical suppression system 
was specified. 

AFFF Subsystem 

The AFFF subsystem contains a main control valve, a water 
pressure and flow control unit, a concentrate bladder tank, 
a water-concentrate proportioned and a distribution system 
of pipe and nozzles. 

The pneumatic pressure from the control unit operates the 
main control valve of the AFFF subsystem, initiating water 
flow from the mine water supply line. The flow and pressure 
of th'rs line are maintained at constant levels through the use 
of a pressure-reducing valve. This flow of water is used to 
fill the volume of the bladder tank between the bladder and 
the tank wall, pressurizing the concentrate inside the blad- 
der. The concentrate is then forced out of the tank and into 
the proportioned where it is mixed with the main water flow 
to yield a solution containing concentrate. The solution then 
flows through the piping to the nozzles, where air is drawn 



into it to form the foam that is discharged onto the 
hazard. 

Eight standard nozzles, each providing 100 sq ft of 
coverage, are required to cover the fueling area. At the re- 
quired minimum delivery rate of 0.1 gpm/sq ft of protected 
area, the 800-sq-ft fuel storage area would require 80 gpm 
of foam discharge. A minimal 10-min discharge would require 
a 24-gal AFFF concentrate tank. Increasing the pressure of 
the foam-water sprinkler nozzle to 30 psi to provide a higher 
quality foam would yield 16 gpm per nozzle or 0.16 gpm/sq 
ft of area. The 800-sq-ft area would then require a 128-gpm 
discharge and a 40-gal AFFF concentrate tank for a 10-min 
discharge. Utilizing a 70-gal concentrate tank and operating 
eight nozzles at 16 gpm per nozzle, the actual foam flow time 
would be 18.2 min. The distribution piping was hydraulically 
calculated and sized to provide nearly equal nozzle pressures 
to all eight nozzles. 

The AFFF agent used in this system is a 3-pct-type con- 
centrate intended for use by dilution or proportioning at a 3:97 
volume ratio with water. At present, there are no Federal or 
military specifications covering this type of concentrate. 
Specification MIL-F-24385A, 2 May, 1977 (U.S. Navy), covers 
6-pct AFFF concentrates and requires performance at 3-pct, 
6-pct, and 50-pct concentrations before and after aging for 
10 days at 150° F of both the concentrate and premixed fresh 
and salt water solutions. 

The concentrate used in this system meets all of the fire- 
performance requirements specification of MIL-F-24385A. It 
also has been tested and found to perform equally well in 
water having a hardness (calcium and magnesium) of 500 
ppm. The AFFF concentrate is a mixture of fluorochemical 
surfactants, hydrocarbon surfactants, and solvents. It is 
specifically formulated to have low corrosion characteristics 
on most common metals and a low environmental impact. 

The nozzles are aspirating-type, upright foam-water 
sprinkler nozzles with 1/2-in NPT connections and a 3/8-in 
throat. They provide good-quality foam during discharge. 



11 




FIGURE 9.— Prototype fire sensing and suppression system for underground fuel storage and transfer area. 



The AFFF system is designed for an operating temperature 
range of 32 : to 1 20 ■ F. This system should not be used where 
temperature may drop below 32° F because the AFFF solu- 
tion will freeze. 

Corrosion protection is accomplished with bronze valves 
and fittings and brass piping, and the entire unit has a special 
epoxy coating. 

Dry Chemical Subsystem 

The dry chemical subsystem consists of three major com- 
ponents: the nitrogen power supply, the dry chemica; storage 
container, and the distribution system composed of piping 
and nozzles. Pneumatic pressure from the control-unit car- 
tridge opens all nitrogen cylinders simultaneously, releasing 
the nitrogen through pressure regulators to pressurize the 
storage container and fluidize the dry chemical. When the 
storage container reaches a predetermined pressure, a frangi- 
ble disc in the outlet piping bursts, releasing the dry chemical 
into the piping. Pre-aimed stationary nozzles discharge the 
dry chemical onto the hazard. 

The dry chemical tank provides for the storage of 425 lb 
of agent. The agent is suitable for use on fires involving 
cellulosic-type fuels such as wood, paper, plastics, etc., as 
well as flammable and combustible gases and liquids. Federal 
Specification 0-D-1380A. July 12, 1968 (General Services Ad- 
ministration), details the composition and physiochemical 
properties of the type of agent used. The agent is a finely 
divided solid cnsisting of about 90 wt pet monoammonium 
phosphate. The remaining 10 pet consists of materials to im- 



prove flow and packing characteristics and reduce 
hygroscopicity such as clays, colloidals, silicas, and polymeric 
siloxzines. This agent is compatible with AFFF in a separate 
or simultaneous application. 

The four 1-1/2-in dry chemical nozzles provide a fan-shaped 
pattern for a large-area sweep and will distribute the dry 
chemical at a flow rate of about 12 Ib/s. The distribution pip- 
ing for the dry chemical subsystem is schedule 40 hot-dipped 
galvanized pipe. A balanced piping arrangement is used to 
distribute the dry chemical evenly to each of the four nozzles. 

The dry chemical subsystem is designed for and can be 
operated in the temperature range of -40° to 120° F. 

All components have a heavy external epoxy coating for 
protection against highly humid or corrosive atmospheres. 
The system is completely sealed to prevent internal corrosion. 

Detection and Control 

The detection and control subsystem contains ultraviolet 
detectors monitored by a control panel that provides a 
pneumatic output to the suppression subsystem when flames 
are present within the cone of vision of the detectors. 

The detectors are self-contained 24-V dc units that provide 
both instantaneous and time-delayed contacts as outputs. 
The control system utilizes 5-s-delay contacts as a zone-alarm 
input, leaving the instantaneous contacts available for addi- 
tional remote annunciation on an individual-detector basis if 
required. The detectors are equipped with an "optical integri- 
ty" feature that allows remote testing of the condition of their 



12 



optical lenses. The detectors are housed in an explosion-proof 
enclosure and are easily installed with integral swivel mounts 
and brackets. 

Two detectors are required for this system. They are posi- 
tioned in the fueling area so their 90° fields of vision overlap, 
with each detector covering the entire area. The two detec- 
tors are cross-zoned within the control unit— meaning that 
both detectors must sense the fire before the fire signal 
passes to the actuation device— to minimize false alarms. 

The fire signal operates a mechanical device that releases 
an internally stored pressurized gas to operate the suppres- 
sion subsystem. The control unit has an internal adjustable 
time delay to delay actuation of the suppression system un- 
til a predetermined time has elapsed after the alarm input 
is received. It also has an abort function to permit system 
maintenance without nuisance alarms. 



TESTS 

Laboratory Component 
Testing 

All system components were analyzed for their suitability 
for use in a harsh underground mine environment. For com- 
ponents with insufficient histories of performance in 
underground environments, tests were performed in the 
laboratory under simulated mining conditions. 

Suppression 

AFFF subsystem components were selected with corrosion 
resistance as the major consideration. Components not nor- 
mally used in AFFF systems, such as the main control valve 
and pressure-reducing valve, were chosen based on materials 
of construction and simplicity of operation. Since little data 
was available on the performance of the main control valve 
and pressure-reducing valve under the conditions anticipated 
in the mine, specialized performance tests were devised and 
conducted for these components. 

Operational testing on the pneumatically operated main 
control valve consisted of obtaining the torque output from 
the actuator before and after prolonged corrosion testing in 
a salt spray. The result of the salt spray was a decrease in 
torque output significant enough to cause concern. Therefore, 
a new actuator was obtained and modified to prevent cor- 
rosive atmospheres from affecting the internal parts of the 
actuator. Gaskets and plugs were used to seal joints, and 
0-rings were added to the actuator shaft to eliminate seepage 
between the shaft and body. A second salt-spray test on the 
redesigned actuator gave satisfactory results. 

The objective of the pressure-reducing valve tests was to 
determine pressure setting versus flow and pressure. No 
operational problems were encountered during any of the 
tests. The pressure-reducing valve provided leak-free opera- 
tion and consistently reduced pressures downstream. 

Due to previous testing and past performance in actual use, 
the dry chemical subsystem was considered to be rugged 
and corrosion resistant enough to withstand the atmosphere 
and hard usage it would encounter underground. Com- 
ponents of the system such as cylinders, valves, hoses, 
gauges, and other equipment have all undergone salt-spray, 
shock, vibration, and operational tests to obtain listings by 
Underwriters Laboratories, Inc., and Coast Guard marine ap- 
proval. Dry chemical installations on offshore platforms are 
exposed to severely corrosive environments, yet they func- 
tion for extended periods without failure. 



Detection and Control 

All of the component parts of the detection and control sub- 
system have been extensively tested and are listed by Under- 
writers Laboratories. The ratings and limitations of the detec- 
tion system and the capabilities of the emergency power 
supply and control equipment are predefined by Underwriters 
Laboratories. 

Laboratory Full-Scale Fire Testing 
of Complete System 

As a last step prior to in-mine installation and testing, the 
complete prototype system was subjected to full-scale fire 
tests in a specially designed fire-test fixture. 

The fire hazard consisted of a 50-sq-ft pan fueled with 2 
in of heptane. Heptane was used instead of diesel fuel for 
ease of ignition and also because it has a much hotter flame 
and is more difficult to extinguish. A vehicle mockup was 
situated directly over the pan to simulate a fire under a vehi- 
cle during the refueling operation and to provide an obstacle 
to fire-suppressant agent coverage. 

The AFFF subsystem was installed with four nozzles 
spaced 10 ft apart in a grid and suspended 10 ft directly over 
the hazard. The dry chemical unit was installed with two of 
the four nozzles aimed at the hazard. System actuation was 
provided by pneumatic actuation lines running from the AFFF 
and dry chemical subsystems to the control unit. The con- 
figuration of system elements for mockup testing is shown 
in figure 10. 

The heptane was ignited and allowed approximately a 15-s 
preburn, which gave total fuel involvement. At 15 s, one detec- 
tor was aimed at the fire; it instantaneously actuated the con- 
trol unit. Flow from the AFFF subsystem began 
immediately— pure water for the first 5 s and, once stabilized, 
foam thereafter. The cooling effect of the foam decreased 
flame intensity slightly. 

When the AFFF control valve was opened, the nitrogen 
cylinder valves on the dry chemical unit simultaneously 
opened, beginning pressurization of the dry chemical tank. 
A 12-s delay was built into the dry chemical unit by use of 
the frangible disc, allowing pressure to build in the tank and 
fluidize the dry chemical 

The time span between the bursting of the disc and com- 
plete extinguishment (fig. 1 1) was approximately 3 s. The total 
time from detection to extinguishment, during which foam flow 
had already begun, was approximately 15 s. 

Additional tests were conducted to determine the effec- 
tiveness of AFFF and dry chemical used separately on spill 
fires obstructed from the overhead nozzles by the vehicle 
mockup. Neither AFFF nor dry chemical alone was able to 
extinguish such a fire. 

Field Test 

The site selected for field tests was a fuel dock in Union 
Carbide Corp.'s Pine Creek tungsten mine near Bishop, CA. 
A description of this site is provided in table 5. The complete 
sensing and suppression system was disassembled, shipped 
to the mine site, installed, debugged, and fire tested in the 
mine. 

Installation, Inspection, and Pretests 

Underground installation took 5 days and proceeded as 
planned with no major difficulties. The installation of the 
detection and control subsystem (figs. 12-13) was completed 
first, and detector performance was monitored for several 



13 




FIGURE 10.— Configuration of system elements for mockup testing. 






FIGURE 11.— Twin-agent discharge during mockup testing. 



days prior to the fire tests. Temporary equipment installed 
included a switch to prevent premature firing of the system 
while the test fires were being ignited. 
During 3 days of monitoring, no false alarms or other prob- 



lems occurred. On the fourth day, a malfunction was 
discovered in an unused portion of the time-delay circuit. The 
cause was determined to be the temperature-humidity effect 
of the underground atmosphere. A simple bypass of the cir- 



14 



TABLE 5.— Test site description 

(Fuel dock in Pine Creek tungsten mine) 

Parameter Quantity 

Environment: 

Ventilation fpm . . 90 

Temperature °F . . 40-45 

Humidity pet . . 90-1 00 

Dimensions: 

Area sq ft . . 750-800 

Height ft. . 10 

Flammables, gal: 

Diesel fuel 1 35 

Motor oil 110 

Hydraulic oil 110 

Class A None 

Water supply: 

Static pressure of 4-in main supply (nominal) psi. . 200 

Total hardness mg/L . . 28.0 

pH 7.1 

Electrical supply (for 3 200-W explosion-proof lamps): 

Voltage V. . 110 

Current A . . 20 




FIGURE 12.— System control panel. 




FIGURE 14.— Twin-agent suppression subsystem 
(exclusive of distribution network). 



cuit solved the problem; however, a new circuit board that 
included a permanent solution to this problem was later 
installed. 

The AFFF-dry chemical suppression module (fig. 14) was 
positioned adjacent to the fuel dock. Dry chemical and foam 
piping networks (figs. 15-16) were cabled to roof bolts and/or 
J-bolts. 

Following installation, the system was checked out by 
means of scheduled pretests. Prior to the fire tests, the system 
was given a complete maintenance inspection and discharge 
test. The detectors were checked from the test panel and also 
by using a cigarette lighter flame. All cartridge actuators were 
operated to assure leak-free tubing and normal actuation. A 
50-lb discharge of the multipurpose dry chemical was initiated 
to assure proper fluidization of the dry chemical, proper 
frangible-disc rupture, and proper nozzle location and aim. 

During the last actuation sequence, pressure gauges were 
installed at the water inlet and at one nozzle. Static inlet 
pressure was 210 psi from the 4-in mine water supply line. 
Flow pressure at the inlet was 55 psi, but the distribution- 





FIGURE 13.— Ultraviolet flame detector head. 



FIGURE 15.— Dry chemical nozzle with blowoff cap. 



15 




FIGURE 16.— Foam-water sprinkler nozzle. 



piping head loss lowered the nozzle flow pressure to 12 psi. 
The pressure-reducing valve setting was increased in an at- 
tempt to obtain the desired nozzle pressure of 30 psi. 
However. 1 2 psi was the maximum nozzle pressure attained 
during stabilized flow. At 12 psi, the nozzle pressure-flow 
curve indicates a flow rate of 10.5 gpm. This flow rate is barely 
enough to maintain the minimum required foam flow of 0.1 
gpm/sq ft. 

Fire Testing 

Since Federal mine safety regulations (30 CFR 57.4-58) pro- 
hibit the lighting of fires underground, it was necessary to 
obtain a variance in order to perform the field testing. Both 
the Mining Enforcement and Safety Administration (now 



MSHA) and the California Department of Industrial Relations 
granted the necessary variances. The field testing was per- 
formed in accordance with these variances. 

Using a temporary switch added to the control panel, the 
automatic suppression system discharge circuit was rendered 
inoperable. Fires could thus be permitted to grow to full in- 
volvement before suppressant discharge. (If operated in the 
automatic mode, the detectors would have sensed the fire 
instantly, and suppression would have begun before full in- 
volvement of the fuel.) 

The first underground fire test was the extinguishment of 
a 2- by 3-ft pan fire placed (unobstructed) on the fuel storage 
pad. The pan contained approximately 2 gal of water sup- 
porting 1 gal of diesel fuel. For this test, the dry chemical sub- 
system was disconnected and only the foam system was ac- 
tuated. After ignition and a 15-s preburn time, the AFFF 
system was manually actuated. The fire was completely ex- 
tinguished in 10 s. 

The second fire test was conducted utilizing the same pan 
and the same amounts of water and fuel. The pan was placed 
under the vehicle mockup to simulate an obstructed spill 
under a vehicle (fig. 17). The fuel was ignited (fig. 18) and 
was fully involved 10 s after ignition (fig. 19). The AFFF system 
was manually actuated, and the drychemical system frangi- 
ble disc ruptured 13 s later (fig. 20). Complete extinguish- 
ment was achieved 3 s after actuation of the dry chemical 
system (fig. 21). 

Carbon monoxide sampling was performed following each 
test, however, measurable quantities could not be detected. 
After 43 months of reliability testing in the mine with the 
system operating in the automatic mode, no problems have 
been encountered. 




FIGURE 17.— Vehicle mockup in fuel transfer area. 



16 







FIGURE 18.— Igniting test fire beneath vehicle mockup. 




FIGURE 19.— Test fire burning under mockup. 



17 




FIGURE 20.— Twin-agent discharge onto test fire. 




FIGURE 21.— Test fire fully extinguished. 



18 



STUDIES OF ALTERNATIVE SYSTEM DESIGNS 



As noted previously, mines vary so widely in extraction 
methods, layout, ventilation plans, equipment selection, etc., 
that no single fueling area fire protection system design is 
universally applicable. Each fueling system needs to be in- 
dividually analyzed for fire hazards and appropriate fire safety 
measures specified. However, the generic fire protection 
system design concepts developed through this research are 
intended to be flexible enough to adapt to a wide variety of 
conditions. In order to evaluate the applicability of these 



generic design concepts to a wide range of mine settings, 
a second fueling area fire protection system was installed in 
a high-back room-and-pillar lead mine in Missouri, and "paper 
studies" of other potential system configurations were per- 
formed. The second system has functioned properly for 16 
months, and the paper-study results show that the generic 
design concepts can be applied to nearly any fueling system 
layout. 



COST-EFFECTIVENESS ANALYSIS 



The cost effectiveness of fire control systems can be 
analyzed in many ways. Two common approaches are to con- 
sider (1) the cost of the system versus the cost of potential 
fire losses and (2) cost-performance tradeoffs between 
various types and configurations of systems. 



SYSTEM COST VERSUS FIRE COST 

Numerous quantitative methods are available to assist risk 
managers in comparing the cost of various risk-management 
tools (e.g., a fire control system) to the cost of sustaining a 
particular loss (e.g., a fire). These quantitative methods re- 
quire numerous inputs, but most important are estimates of 

(1) the probability of the occurrence of a particular loss and 

(2) the magnitude of potential losses. 

Although the magnitude of potential losses is easily deter- 
mined, an estimate of the probability of occurrence can re- 
quire considerable effort. These estimates are generally 
based on industrywide long-term loss experiences or 
calculated using complex predictive techniques such as fault- 
tree analysis, failure modes and effects analysis, and criticality 
analysis. 

Estimates of the probability of occurrence and magnitude 
of losses are combined to yield an "expected annual loss." 
Various risk-management tools such as insurance, coin- 
surance, hazard reduction, and installation of safety devices 
are then evaluated in light of the "expected loss." Other fac- 
tors which are difficult to quantify, and therefore difficult to 
consider through quantitative methods— such as the poten- 
tial for casualties and the need to maintain a certain produc- 
tion level— may also profoundly influence the development 
of a risk-management strategy. If the fire hazards analysis 
indicates that personnel safety may be threatened, precau- 
tions such as redesign of the fueling area and/or automatic 
fire protection system are appropriate, regardless of the out- 
come of any system-cost-versus-f ire-cost analyses. 

Since no large-scale fueling area fires have occurred, no 
industrywide loss experience exists, and a calculation of loss 
probabilities using a predictive technique is beyond the scope 
of this report. Thus, a case-study example illustrating these 
principles is not provided. However, even with mine shutdown 
costs of as little as $85,000 per day, a probability of the oc- 
currence of fire as low as 0.3 pct/yr (the equivalent of one 



fire every 333 yr), and no other cost factors considered, a 
complete automatic fire sensing and suppression system 
would be an economically attractive loss-control option. 

COST-PERFORMANCE TRADEOFFS 
BETWEEN SYSTEMS 

The primary purpose of an underground fueling area fire 
sensing and suppression system is to reduce the safety 
hazard posed by a potential fueling area fire. Once the need 
for fire protection is established, however, an analysis of cost 
versus performance between various system options will per- 
mit selection of the most cost-effective approach to achieve 
the safety level desired. 

Numerous techniques are available to measure cost effec- 
tiveness. The following example is provided to illustrate the 
application of one such method to a specific fueling system 
configuration. 

Six types of fire protection systems are considered in this 
example: water, high-expansion foam, AFFF, Halon 1301, dry 
chemical, and twin agent. The analysis is based on an 
unenclosed fuel transfer area 65 ft long, 20 ft wide, and 13 
ft high with moderate-to-high ventilation, with the following 
stipulations: Combustible-liquid spill fires as well as running- 
fuel and pressure fires could occur. No ordinary combustibles 
materials are stored in the area. All systems, except the water 
system, include cross-zones ultraviolet detection. 

The cost-effectiveness analysis is accomplished in three 
steps as shown in table 6. First, each fire protection system 
is evaluated for effectiveness by assigning effectiveness 
points (Pt) from to 800 for each evaluation criteria, multiply- 
ing the Pt value by a weighting factor (Wt) from 1 to 3, and 
summing the resulting ratings (Rt) for each evaluation criteria 
to yield a system effectiveness rating. Second, the cost of 
each type of system (including installation cost) is determined. 
Third, the system effectiveness rating is divided by the cost 
to yield a cost effectiveness index for each system. 

The potential range of cost-effectiveness indexes for this 
example is (no system effectiveness) to 1 .41 (highest possi- 
ble system effectiveness rating divided by lowest system 
cost). In this example, one system type, twin agent, has both 
the highest effectiveness rating and the highest cost- 
effectiveness index. 



19 



TABLE 6.— Cost-effectiveness matrix for fueling area fire protection systems 





System type 




Water 


High-expansion foam 


AFFF 




Pt 


wt 


Rt 


Pt 


Wt 


Rt 


Pt 


Wt 


Rt 


Evaluation criteria: 
Suppressant effectiveness 
for— 

Class B spill fire 

Class B pressure fire 

Class B running-fuel fire. . . . 

Class A fire 

Extinguishing time. 


200 


500 
100 
400 


3 
3 
3 

1 
2 

1 


600 


500 
200 
400 


300 

200 
300 
400 
300 


3 
3 
3 
1 
2 
1 


900 

600 
300 
800 
300 


800 
200 
300 
800 
400 
400 


3 
3 
3 
1 
2 
1 


2,400 
600 
900 
800 
800 


Effects on personnel 


400 


System effectiveness rating 

System cost 

Cost-effectiveness index 


1.700 

$7,350 

023 


2,900 

$10,900 

0.27 


5,900 

$10,600 

0.56 




Halon 1301 


Dry chemical 


Twin agent 




Pt 


Wt 


Rt 


Pt 


Wt 


Rt 


Pt 


Wt 


Rt 


Evaluation criteria 
Suppressant effectiveness 
for— 
Class B spill fire 
Class B pressure fire 
Class B r u nnmg-fuel fire 
Class A fire 
Extinguishing time 
Ejects on personnel 






500 
300 


3 
3 
3 
1 
2 
1 






1,000 
300 


400 
400 
400 
400 
500 
400 


3 
3 
3 
1 
2 
1 


1,200 
1,200 
1,200 

400 
1,000 

300 


800 
800 
800 
800 
500 
400 


3 , 

3 

3 

1 

2 

1 


2,400 
2,400 
2,400 

800 
1,000 

400 


System effectiveness rating 
System cost 
Cost-effectiveness index 


1,300 

$10,300 

0.13 


5,300 

$10,300 

0.51 


9,400 

$16,500 

0.57 



Pt Effectiveness points (0-800). 



Wt Weighting factor (1-3). 



Rt Resulting rating (Pt x Wt). 



SUMMARY 



In response to the growing fire safety hazard posed by 
underground fuel storage and fuel transfer areas, the Bureau 
has developed guidelines for safe and efficient fueling system 
designs, prepared specifications for automatic fire sensing 



and suppression systems for these areas, successfully con- 
ducted laboratory and in-mine fire tests of prototype systems, 
and conducted cost-effectiveness evaluations of various fuel- 
ing area fire protection system designs. 



irU.S. CPO: 1983-50S-019/20.079 



INT.-BU.OF MINES, PGH..P A 2B062 



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